Selective excitation of resonance-enhanced multiphoton-ionization photoelectron spectroscopy via a cubic phase modulation

Resonantly enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PS) has proven to be a well-established tool to study the excited-state structure. However, femtosecond-induced REMPI-PS suffers from poor selectivity between neighboring excited states due to the large spectral bandwidth. In this paper, we present a feasible scheme to realize the selective excitation of (2+1) REMPI-PS in sodium atoms. We show that, by shaping the femtosecond laser pulse with a cubic phase modulation, a high-resolution (2+1) REMPI-PS is obtained, and the (2+1) REMPI-PS signal from one excited state is enhanced while that from the other excited state is effectively suppressed. Furthermore, we explain the physical control mechanism of the selective excitation of (2+1) REMPI-PS by considering the two-photon power spectrum.